Jerry Dipoto says he’ll gladly go to YouTube and watch a major league baseball game from 40 years ago.

But the game is a bit different now: Starters typically go five or six innings, and all of them throw in the mid-90s.

And the Mariners plan use a starting rotation of six pitchers this year. Who would have thought of such a thing 40 years ago?

“That is something we will employ at some time this year,” Dipoto said.

Why?

Because there are fewer starters throwing 200 innings every year. And the ones who can are generally the most expensive on the free-agent market. Notice how you haven’t seen the Mariners chasing after the bevvy of starters still available to sign?

Dipoto said the Mariners have been setting themselves up or two years to be versatile enough with their position players to include 13 pitchers as part of their 25-man roster, giving them the flexibility to add a sixth starter to the rotation or extra bullpen depth.

“You might not see us break out of camp that way, but at some point during the season we could pull back and put an extra guy in the rotation,” Mariners manager Scott Servais said.

“But to do that, you got to have six guys that you feel comfortable about giving the ball to, and not just run out there. But you’re only lasting 2⅓ or 3⅓ innings. So you got to not just have the quantity, but the quality to do it. It’s something we think we can do.”

So what does that look like?

Felix Hernandez, James Paxton and Mike Leake are locks, barring injuries, for the first three rotation slots (though the order might be up in the air).

The Mariners have three off-days in their first nine days of the season. But that six-man rotation might especially come into effect, say, during a 20-game stretch without an off-day from the end of July into August.

There are more off days in the 2018 schedule, but there are still five spans of 10-plus consecutive games. Though the problem with a six-man rotation is that the team aces get fewer starts.

“That’s something we don’t want to do until the circumstances dictate we have to,” Dipoto said. “We aren’t going to cut our pitchers short if they’ve shown us the ability to get through six or seven innings.”

But part of the reasoning – if not the primary reason – is health.

The Mariners had to use 17 starting pitchers last year – the most in the major leagues and tied with the inaugural 1977 season for the most in club history. And both Felix and Paxton made two trips each to the disabled list.

Mariners starter Mike Leake, left, receives a ball from catcher Mike Zunino during a game last August at Safeco Field. The Mariners said Leake's durability and reliability made him an attractive pitcher to acquire last summer.(Photo: Joe Nicholson-USA TODAY Sports)

They began the year planning a rotation of Hernandez, Paxton, Drew Smyly, Hisashi Iwakuma and Yovanni Gallardo. And you saw how that turned out. None of them threw more than 136 innings, with Ariel Miranda leading the team with 160 innings pitched.

In 2001, the last time the Mariners reached the postseason, they had four pitchers who logged more than 160 innings, and three with more than 200 (Freddy Garcia, Aaron Sele and Jamie Moyer).

Then again, the Astros won the World Series last season without any pitchers logging more than 160 innings. And the team they beat, the Dodgers, had just one (Clayton Kershaw).

“A guy like James Paxton, when he’s on let him go until he stops,” Servais said. “But it’s almost without exception that pitchers are worse the third time through the lineup.”

In 2017, the Mariners had a player age 26 or younger pitch about one in every three innings (429⅔ of 1,440⅓ innings).

“Sometimes we will consider going into the game that it’s going to be a 15-out appearance,” Dipoto said. “If one of every three of your innings is being thrown by rookies, you are trying to throw them a life preserver.”

Gonzales seems to enter camp as the favorite for a spot in the rotation, especially considering the left-hander is out of minor-league options. But instead of expecting he and Ramirez to get through six innings, the Mariners could bridge them with their deeper bullpen, and sliding in someone like Miranda or Moore as a sixth starter when needed.

Marco Gonzalez, who is out of minor league options, is likely to claim a spot in the Mariners' rotation.(Photo: Evan Habeeb-USA TODAY Sports)